Physical and genetic characterization of the genome of Lactobacillus lactis bacteriophage LL-H

Abstract

Bacteriophage LL-H is a virulent phage of Lactobacillus lactis LL23. A restriction map of the phage genome was constructed with various restriction endonucleases. This chromosome has a 34-kilobase size and seems to be circularly permuted. We used a bank of LL-H restriction fragments to study the expression of five of the seven main phage particle proteins. Immunoblotting experiments permitted the mapping on the chromosome of several genes coding for phage particle proteins. We also show that the gene of the main capsid protein is expressed from its own promoter in an Escherichia coli strain.

Ribosome binding site consensus sequence of Lactobacillus delbrueckii subsp. lactis bacteriophage LL-H

“…The probable explanation for their expression is translational coupling. These ORFs included for example one that coded for a previously localized structural protein [5].…”

“…Its genome is double-stranded DNA, which is circularly permuted and terminally redundant. [5,6]. During their evolution phages have become well adapted to the genetic systems of their hosts [7].…”

Bacteriophage and bacteriophage resistance in lactic acid bacteria

“…The lytic bacteriophage &LL-H is active against Lactobacillus lactis LL23 [26]. It has a circularly permuted dsDNA genome of 34 kb, and has been mapped with a number of restriction enzymes.…”

“…The gene shares no homology with other sequences deposited in the databanks. However, the protein is similar in size to the 35-kDa major head protein of the lactobacillus phage &LL-H [26]. The &F4-1 mop gene has been used as the target for an antisense RNA strategy which is described below.…”

Prospects for the genetic manipulation of lactobacilli

“…Two phages of L. casei have been extensively characterized [33,34]. The genome of an L. bulgaricus phage has been analysed by molecular cloning in E. coli [35]. A virulent phage of L. casei causing off-fermentation of milk was found to have a genome differing from the prophage genome found in the chromosome of the starter strain only by the presence of a 1.3 kb insert of DNA [36].…”